Why does internal storage keep growing over the time for no reason? At some point it becomes simply impossible to update apps, due to lack of sufficient memory space. Not even cache cleanup can save it, and I have moved as many apps as I could to SD card with no help.

Apps need to be uninstalled then installed again on every update. Depending on the app this is problematic since they have lots of custom settings, and I have never seen that automatic Google servers backup and restore working whenever I needed it. Fortunately for stock preloaded apps your settings are not lost, since you can just remove updates since stock version, not remove it.

This indicates one of the main causes of this problem at least: app updates are somehow incremental, and performing the above workaround will somehow save some space, with same result of app updated to latest version. So innocent everyday app updates are no reason for causing internal storage to fill up.

What workarounds can I do in order to overcome this problem, besides the obvious ones like removing stuff or buying a new phone? I think I heard about re-partitioning phone memory to make internal storage point to external SD card, but I wonder if it will make things too much slower, for example. Please, point me to good solutions, even if they require rooting.

things on computers do not happen "for no reason". Either you are installing more apps, or the apps you have are writing data/files to the internal storage over time which is filling it up.
– FoamyGuyMay 19 '13 at 4:20

I obviously am not installing more apps, and if they are writing data over the time, then that should be easily detected by App2SD through the app data field. Unless there's more app data than, ugh, the app data.
– Renato SilvaMay 19 '13 at 5:04

5 Answers
5

Before you can fix the issue you have to identify the cause. We have a few answers that deal with tracking down storage usage. But usually they target the external storage/SD-card. Here we are dealing with the internal storage, which is usually protected from normal user access and hence it's good (if not required) to have root. But other then that, the tools mentioned in the question should give you a good idea of how your internal storage is used:

Summarizing the answers and comments on a more objective approach. Please edit this and add any verified procedure that objectively may help with this annoyance.

You could try the obvious things like removing unused apps, cleaning up system cache, etc.

If your phone is rooted, Link2SD helps a lot by creating symlinks from original app locations to the SD card. Android will think the apps are on internal storage, but in fact they are just linked there, real location is the SD card. Specific apps, the biggest ones, can be selected for the linking process.

You may try removing updates from stock preloaded apps, for only then updating to the latest version directly. These apps seem to take more and more storage while getting updated over time. That was my case with Facebook for example, one of the most problematic about storage usage. This workaround should not delete app settings, since app cannot and will not get uninstalled at all.

"Please edit this and add any verified procedure that objectively may help with this annoyance" -- that permission is extended to a Wiki answer. So may be you wanna convert this one into a Wiki, because edit to someone's answer (non-wiki) would probably be rejected by reviewers even if you've mentioned a note.
– Firelord♦Jul 31 '15 at 11:04

Every time an app gets updated, an old copy of the app is retained somewhere. You can see that in settings > apps > select an app, and you can see uninstall updated option. So whenever I have an updated app, I simply delete the old app and install the new app.

I recommend not to use this method which saves data internally. Other apps like Facebook, Whatsapp can be done.

The second phrase is difficult to understand. What are you trying to say? That the user should not use the method for apps that save the data internally, and that it should only be used for other apps like Facebook and Whatsapp?
– geffchangSep 21 '13 at 9:32

"Every time an app gets updated, an old copy of the app is retained somewhere." is not true for most apps. AFAIK it's only true for system apps. Your recommendation of uninstalling an app before updating will result in loss of all settings of the app (if those settings are clouded synced, which is also true for most app).
– FlowSep 21 '13 at 9:35

I have this problem just now, it keep popup "internal storage almost full". The storage doesn't match with total space, i.e. it shows I used more than 15GB over total 16GB, but all categories sum up only ~11GB. I tried delete a lot of apps and folder but only 0.5GB free.

Eventually I realized I don't shutdown phone for many days, so I simply shutdown and reboot, and then it able to shows the correct free space 4.41GB!

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